A Phase 2a, Randomized, Placebo Controlled, Study to Evaluate the Safety and Efficacy of AMG 557/MEDI5872 in Primary Sjögren's Syndrome

This is a Phase 2a, multicenter, randomized, double-blind, placebo-controlled, parallel-group
study to evaluate the clinical and biologic efficacy, as well as the safety of SC doses of
AMG 557/MEDI5872 in adult subjects with Primary Sjögren's Syndrome.

Inclusion Criteria:

- Age 18 through 75 years at the time of signing the ICF.

- Fulfill American-European Consensus Group (AECG) criteria for pSS

- ESSDAI score ≥ 6.

- Positive anti-SS-A and/or anti-SS-B autoantibodies and at least IgG > 13 g/L or RF
level > upper limit of normal (ULN) or positive test for cryoglobulins

- Willingness to undergo protocol-required minor salivary gland biopsies.

- Negative TB test during screening

- Immunization up to date as determined by local standard of care.

Exclusion Criteria:

- Previous treatment with AMG 557/MEDI5872.

- Evidence of signs or symptoms of a viral, bacterial, or fungal infection within 2
weeks (14 days) prior to randomization (Day 1) according to the assessment of the
investigator; any infection requiring IV antibiotic or antiviral treatment within 8
weeks of randomization (Day 1); history of herpes zoster within 3 months prior to
randomization (Day 1).

- Evidence of significant renal insufficiency

- Positive test at screening for hepatitis B, hepatitis C, or human immunodeficiency
virus (HIV) antibody.

- Prior administration of any of the following:

1. Belimumab in the past 6 months prior to randomization (Day 1);

2. Rituximab in the past 12 months or CD19+ B cells < 5/µL if rituximab treatment
was more than 12 months prior to randomization (Day 1);

3. Abatacept in the past 6 months prior to randomization (Day 1);

4. Tumor necrosis factor inhibitors (adalimumab, certolizumab, etanercept,
golimumab, infliximab) in the past 3 months prior to randomization (Day 1);

5. Tocilizumab in the past 3 months prior to randomization (Day 1);

6. Cyclophosphamide (or any other alkylating agent) in the past 6 months prior to
randomization (Day 1); cyclosporine (except for eye drops), tacrolimus,
sirolimus, mycophenolate mofetil, azathioprine, or leflunomide in the past 3
months prior to randomization (Day 1).

- Receiving any of the following:

1. Corticosteroids: > 10 mg/day oral prednisone (or equivalent); Any change or
initiation of new dose within 4 weeks prior to signing the ICF through
randomization (Day 1); Intramuscular, IV, or intra-articular corticosteroids
within 4 weeks prior to signing the ICF through randomization (Day 1); Any change
or initiation of new dose of topical corticosteroids within 2 weeks prior to
signing the ICF through randomization (Day 1);

2. Antimalarials: any increase or initiation of new dose of antimalarials (eg,
chloroquine, hydroxychloroquine, quinacrine) within 12 weeks prior to signing the
ICF through randomization (Day 1).

3. Methotrexate: > 20 mg/week methotrexate; Any change or initiation of new dose of
methotrexate within 4 weeks prior to signing the ICF through randomization (Day
1); Any change in route of administration.

4. Any increase or initiation of new dose of regularly scheduled nonsteroidal anti
inflammatory drugs (NSAIDs) within 2 weeks prior to signing the ICF through
randomization (Day 1).

5. Cevimeline or pilocarpine and cyclosporine eye drops (Restasis): any increase or
initiation of new doses within 2 weeks prior to signing the ICF through
randomization (Day 1).